U.S. patent application number 14/890479 was filed with the patent office on 2016-03-31 for multilayered heat-recoverable article, wire splice, wire harness, and method for producing adhesive for multilayered heat-recoverable article.
The applicant listed for this patent is SUMITOMO ELECTRIC FINE POLYMER, INC., SUMITOMO ELECTRIC INDUSTRIES, LTD.. Invention is credited to Yasutaka EMOTO, Ryota FUKUMOTO, Satoshi YAMASAKI.
Application Number | 20160089847 14/890479 |
Document ID | / |
Family ID | 54240255 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160089847 |
Kind Code |
A1 |
FUKUMOTO; Ryota ; et
al. |
March 31, 2016 |
MULTILAYERED HEAT-RECOVERABLE ARTICLE, WIRE SPLICE, WIRE HARNESS,
AND METHOD FOR PRODUCING ADHESIVE FOR MULTILAYERED HEAT-RECOVERABLE
ARTICLE
Abstract
An object of the present invention is to provide a multilayered
heat-recoverable article in which an adhesive layer easily flows
during heat shrinkage to ensure adhesiveness with an adherend and
does not flow out from a base material layer after heat shrinkage,
and a wire splice and a wire harness that include a tube formed by
thermally shrinking such a multilayered heat-recoverable article.
The multilayered heat-recoverable article (1) according to the
present invention includes a cylindrical base material layer (10),
and an adhesive layer (11) formed on an inner circumferential
surface of the base material layer. The adhesive layer (11) is
formed of a resin composition that contains a polyamide as a main
component and that does not substantially contain an inorganic
filler. The resin composition is cross-linked by irradiation with
ionizing radiation. A shear viscosity of the adhesive layer (11) at
150.degree. C. is 300 Pas or more at a shear rate of 0.01 s.sup.-1
and 200 Pas or less at a shear rate of 100 s.sup.-1. The wire
splice and the wire harness according to the present invention
includes a tube formed by thermally shrinking the multilayered
heat-recoverable article (1).
Inventors: |
FUKUMOTO; Ryota; (Osaka,
JP) ; YAMASAKI; Satoshi; (Osaka, JP) ; EMOTO;
Yasutaka; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO ELECTRIC INDUSTRIES, LTD.
SUMITOMO ELECTRIC FINE POLYMER, INC. |
Osaka-shi, Osaka
Sennan-gun, Osaka |
|
JP
JP |
|
|
Family ID: |
54240255 |
Appl. No.: |
14/890479 |
Filed: |
March 24, 2015 |
PCT Filed: |
March 24, 2015 |
PCT NO: |
PCT/JP2015/058894 |
371 Date: |
November 11, 2015 |
Current U.S.
Class: |
174/72A ;
204/157.15; 428/34.9 |
Current CPC
Class: |
B32B 2597/00 20130101;
B32B 2457/00 20130101; H02G 15/1806 20130101; B32B 27/16 20130101;
B32B 2307/206 20130101; B32B 27/08 20130101; B32B 2307/30 20130101;
B32B 2457/04 20130101; B32B 27/34 20130101; B32B 2307/7265
20130101; B32B 2307/736 20130101; B32B 7/12 20130101; H01B 17/58
20130101; B32B 2270/00 20130101; H02G 3/0481 20130101; H01B 3/305
20130101; B32B 1/08 20130101; H01B 3/18 20130101; H02G 3/0462
20130101; H02G 15/043 20130101; H01B 3/441 20130101 |
International
Class: |
B32B 1/08 20060101
B32B001/08; B32B 27/16 20060101 B32B027/16; H02G 3/04 20060101
H02G003/04; B32B 27/08 20060101 B32B027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2014 |
JP |
2014-074566 |
Claims
1. A multilayered heat-recoverable article comprising a cylindrical
base material layer; and an adhesive layer formed on an inner
circumferential surface of the base material layer, wherein the
adhesive layer is formed of a resin composition that contains a
polyamide as a main component and that does not substantially
contain an inorganic filler, the resin composition is cross-linked
by irradiation with ionizing radiation, and a shear viscosity of
the adhesive layer at 150.degree. C. is 300 Pas or more at a shear
rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of 100
s.sup.-1.
2. The multilayered heat-recoverable article according to claim 1,
wherein the resin composition contains a very low-density
polyethylene in an amount of 20% by mass or more.
3. The multilayered heat-recoverable article according to claim 1,
wherein the resin composition contains an ethylene copolymer in an
amount of 20% by mass or more.
4. A wire splice comprising a plurality of wires each of which
includes a conductor and an insulating layer formed on the outside
of the conductor; and a tube adhering to a portion where the
conductors of the wires are connected to each other, wherein the
tube is formed by thermally shrinking the multilayered
heat-recoverable article according to claim 1.
5. A wire harness comprising a plurality of wires each of which
includes a conductor and an insulating layer formed on the outside
of the conductor; and a tube adhering to the wires, wherein the
tube is formed by thermally shrinking the multilayered
heat-recoverable article according to claim 1.
6. A method for producing an adhesive for a multilayered
heat-recoverable article, the adhesive being formed of a resin
composition that contains a polyamide as a main component and that
does not substantially contain an inorganic filler, the method
comprising: a step of irradiating the resin composition with
ionizing radiation, wherein a dose of the ionizing radiation is
controlled so that a shear viscosity of the adhesive at 150.degree.
C. is 300 Pas or more at a shear rate of 0.01 s.sup.-1 and 200 Pas
or less at a shear rate of 100 s.sup.-1.
7. The method for producing an adhesive for a multilayered
heat-recoverable article according to claim 6, wherein the dose of
the ionizing radiation absorbed by the resin composition is 90
kJ/kg or more.
8. The method for producing an adhesive for a multilayered
heat-recoverable article according to claim 6, wherein the ionizing
radiation is an electron beam.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multilayered
heat-recoverable article, a wire splice, a wire harness, and a
method for producing a multilayered heat-recoverable article.
BACKGROUND ART
[0002] Heat-recoverable articles such as heat-shrinkable tubes and
heat-shrinkable caps that have heat shrinkability in the radial
direction are used in covering for, for example, protection,
insulation, waterproofness, and corrosion prevention of a connected
portion of insulated electric wires, a wiring terminal, a metal
tube, or the like. For example, when a connected portion of
insulated electric wires is covered with a heat-shrinkable tube and
heated, the heat-shrinkable tube shrinks so as to conform to the
shape of the connected portion and comes in close contact with the
connected portion. Thus, the heat-shrinkable tube can protect the
connected portion. In the case where high adhesiveness is required
for a connecting portion for the purpose of achieving
waterproofness or the like, a multilayered heat-recoverable article
that includes an adhesive layer formed on an inner circumferential
surface of a cylindrical base material layer is used.
[0003] The adhesive layer of such a multilayered heat-recoverable
article is formed by using a hot-melt adhesive containing an
ethylene-vinyl acetate copolymer (EVA), an ethylene-ethyl acrylate
copolymer (EEA), a polyamide, or the like. Such a multilayered
heat-recoverable article is produced by respectively forming an
outer base material layer and an adhesive layer formed on the inner
circumferential surface of the base material layer by extrusion
molding so as to have a tubular shape, then increasing the diameter
of the resulting tube under heating, and conducting cooling to fix
the shape of the tube. After the extrusion molding, the base
material layer may be cross-linked by irradiation with ionizing
radiation (refer to, Japanese Unexamined Patent Application
Publication No. 2000-129042).
[0004] Adhesion of such a multilayered heat-recoverable article to
an adherend such as an insulated electric wire is performed by, for
example, conducting heating in a state where the multilayered
heat-recoverable article is arranged so as to cover the outer
circumference of the adherend. When the multilayered
heat-recoverable article is heated, the base material layer
thermally shrinks and the adhesive layer fluidizes at the same
time. At this time, the fluidized adhesive layer fills the gap
between the adherend and the heat-shrinkable base material layer.
Accordingly, by solidifying the adhesive layer by the subsequent
cooling, the multilayered heat-recoverable article is brought into
close contact with the adherend.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Unexamined Patent Application Publication
No. 2000-129042
SUMMARY OF INVENTION
Technical Problem
[0006] An adhesive for the multilayered heat-recoverable article is
required to have a high fluidity at the time of heat shrinkage so
as to be in close contact with a recess of the adherend or the like
without a gap. However, if the fluidity is excessively high, the
adhesive flows even when heating is not performed, and the adhesive
may flow out from the base material layer with time.
[0007] Accordingly, an adhesive for a multilayered heat-recoverable
article preferably has thixotropy (thixotropic property) in which
the viscosity decreases when a shear stress is applied, and the
viscosity recovers when the shear stress is removed.
[0008] It is known that thixotropy can be imparted to an adhesive
by adding a filler to the adhesive to form a network formed of a
resin between filler particles. However, in the case of such
thixotropy exhibited by addition of a filler, when a shear is once
applied and the viscosity decreases, the network formed of the
resin is broken. Accordingly, it takes a long time until, after the
shear stress is removed, the network formed of the resin is
reconstructed and the viscosity recovers. Therefore, imparting
thixotropy to an adhesive for a multilayered heat-recoverable
article by addition of a filler may be insufficient in some
cases.
[0009] The present invention has been made in view of the
circumstances described above. An object of the present invention
is to provide a multilayered heat-recoverable article in which an
adhesive layer easily flows during heat shrinkage to ensure
adhesiveness with an adherend and does not easily flow out from a
base material layer after heat shrinkage, and a wire splice and a
wire harness that include a tube formed by thermally shrinking such
a multilayered heat-recoverable article. In addition, another
object of the present invention is to provide a method for
producing an adhesive whose viscosity decreases and which flows
during application of a shear stress, and whose viscosity recovers
immediately after removal of the shear stress, the adhesive being
used for a multilayered heat-recoverable article.
Solution to Problem
[0010] A multilayered heat-recoverable article according to an
embodiment of the present invention includes a cylindrical base
material layer, and an adhesive layer formed on an inner
circumferential surface of the base material layer, in which the
adhesive layer is formed of a resin composition that contains a
polyamide as a main component and that does not substantially
contain an inorganic filler, the resin composition is cross-linked
by irradiation with ionizing radiation, and a shear viscosity of
the adhesive layer at 150.degree. C. is 300 Pas or more at a shear
rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of 100
s.sup.-1.
[0011] A method for producing an adhesive for a multilayered
heat-recoverable article according to an embodiment of the present
invention, the adhesive being formed of a resin composition that
contains a polyamide as a main component and that does not
substantially contain an inorganic filler, includes a step of
irradiating the resin composition with ionizing radiation, in which
a dose of the ionizing radiation is controlled so that a shear
viscosity of the adhesive at 150.degree. C. is 300 Pas or more at a
shear rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of
100 s.sup.-1.
Advantageous Effects of Invention
[0012] According to the multilayered heat-recoverable article
according to an embodiment of the present invention, thixotropy is
imparted to a resin composition of an adhesive layer by
cross-linking. Therefore, a network formed of a resin is not broken
by a shear, and the viscosity recovers, from a state in which the
viscosity is decreased by the shear, immediately after a shear
stress is removed. With this structure, in the multilayered
heat-recoverable article, it is possible to prevent an adhesive
from flowing out from immediately after heat shrinkage. In
addition, according to the multilayered heat-recoverable article,
since the resin composition of the adhesive layer is cross-linked,
a network formed of a resin is not broken and it is possible to
stably prevent an adhesive from flowing out for a long period of
time even in an environment in which a stress is applied from the
outside, or the multilayered heat-recoverable article is exposed to
a high temperature.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is a schematic perspective view illustrating a
multilayered heat-recoverable article according to an embodiment of
the present invention.
[0014] FIG. 2 is a schematic cross-sectional view taken along line
X1-X1 in FIG. 1.
[0015] FIG. 3 is a schematic cross-sectional view taken along line
X2-X2 in FIG. 1.
[0016] FIG. 4 is a schematic cross-sectional view illustrating a
wire splice according to an embodiment of the present invention,
the cross-sectional view corresponding to FIG. 2.
[0017] FIG. 5 is a schematic cross-sectional view illustrating a
wire harness according to an embodiment of the present invention,
the cross-sectional view corresponding to FIG. 2.
[0018] FIG. 6 is a schematic cross-sectional view of the wire
harness illustrated in FIG. 5, the cross-sectional view
corresponding to FIG. 3.
[0019] FIG. 7 is a schematic cross-sectional view illustrating a
multilayered heat-recoverable article according to another
embodiment of the present invention, the cross-sectional view
corresponding to FIG. 2.
[0020] FIG. 8 is a schematic perspective view illustrating a device
for measuring a dripping ratio.
[0021] FIG. 9 is a graph showing the measurement results of the
viscosity of an adhesive for a multilayered heat-recoverable
article in an Example of the present invention for each absorbed
dose of an electron beam.
[0022] FIG. 10 is a graph showing the measurement results of the
viscosity of an adhesive for a multilayered heat-recoverable
article in an Example of the present invention, the Example being
different from the Example in FIG. 9, for each absorbed dose of an
electron beam.
[0023] FIG. 11 is a graph showing the results of a continuous
viscosity measurement of the adhesive for a multilayered
heat-recoverable article shown in FIG. 9, the adhesive being
irradiated with an electron beam at an absorbed dose of 500
kJ/kg.
DESCRIPTION OF EMBODIMENTS
Description of Embodiments of Present Invention
[0024] A multilayered heat-recoverable article according to an
embodiment of the present invention includes a cylindrical base
material layer, and an adhesive layer formed on an inner
circumferential surface of the base material layer, in which the
adhesive layer is formed of a resin composition that contains a
polyamide as a main component and that does not substantially
contain an inorganic filler, the resin composition is cross-linked
by irradiation with ionizing radiation, and a shear viscosity of
the adhesive layer at 150.degree. C. is 300 Pas or more at a shear
rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of 100
s.sup.-1.
[0025] According to the multilayered heat-recoverable article, the
resin composition that forms the adhesive layer contains a
polyamide as a main component and is cross-linked by irradiation
with ionizing radiation, thereby exhibiting thixotropy in which the
shear viscosity significantly decreases when the shear rate
increases. Accordingly, before heat shrinkage, the adhesive layer
of the multilayered heat-recoverable article does not substantially
receive a shear stress and thus does not flow out from the base
material layer. On the other hand, during heat shrinkage of the
base material layer, the adhesive layer is subjected to a shear at
a high shear rate and easily deforms, and thus easily adheres to an
adherend. In addition, since a network formed by cross-linking of a
polyamide is not easily broken by a shear, the viscosity of the
adhesive layer recovers immediately after heat shrinkage is
finished and a shear stress is removed. Therefore, according to the
multilayered heat-recoverable article, it is possible to prevent
the adhesive layer from flowing out from the base material layer
after heat shrinkage.
[0026] The resin composition preferably contains a very low-density
polyethylene in an amount of 20% by mass or more. By incorporating
a very low-density polyethylene, which has a branched structure and
is slightly cross-linked more easily than a polyamide, in the resin
composition that forms the adhesive layer, thixotropy of the
adhesive layer due to cross-linking is significantly improved.
Consequently, the fluidity of the adhesive layer during heat
shrinkage and the difficulty of outflow after shrinkage can be
further accelerated.
[0027] The resin composition preferably contains an ethylene
copolymer in an amount of 20% by mass or more. By incorporating an
ethylene copolymer, which has a branched structure and is slightly
cross-linked more easily than a polyamide, in the resin composition
that forms the adhesive layer, thixotropy of the resin composition
due to cross-linking is significantly improved. Consequently, the
fluidity of the adhesive layer during heat shrinkage and the
difficulty of outflow after shrinkage can be further
accelerated.
[0028] A wire splice according to another embodiment of the present
invention includes a plurality of wires each of which includes a
conductor and an insulating layer formed on the outside of the
conductor, and a tube adhering to a portion where the conductors of
the wires are connected to each other, in which the tube is formed
by thermally shrinking the multilayered heat-recoverable article.
Since the wire splice includes a tube formed by thermally shrinking
the multilayered heat-recoverable article, the adhesive layer has
thixotropy and does not easily flow out from the base material
layer. Accordingly, a state where the tube covers a connected
portion of the wires in a close contact state is maintained, and
thus the connected portion can be continuously protected.
[0029] A wire harness according to another embodiment of the
present invention includes a plurality of wires each of which
includes a conductor and an insulating layer formed on the outside
of the conductor, and a tube adhering to the wires, in which the
tube is formed by thermally shrinking the multilayered
heat-recoverable article. Since the wire harness includes a tube
formed by thermally shrinking the multilayered heat-recoverable
article, the adhesive layer has thixotropy and does not easily flow
out from the base material layer. Accordingly, a state where the
tube is in close contact with the wires to protect the wires can be
maintained.
[0030] A method for producing an adhesive for a multilayered
heat-recoverable article according to another embodiment of the
present invention, the adhesive being formed of a resin composition
that contains a polyamide as a main component and that does not
substantially contain an inorganic filler, includes a step of
irradiating the resin composition with ionizing radiation, in which
a dose of the ionizing radiation is controlled so that a shear
viscosity of the adhesive at 150.degree. C. is 300 Pas or more at a
shear rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of
100 s.sup.-1.
[0031] In the method for producing an adhesive for a multilayered
heat-recoverable article, a resin composition containing a
polyamide is cross-linked by irradiation with ionizing radiation.
Accordingly, it is possible to produce an adhesive for a
multilayered heat-recoverable article, the adhesive having suitable
thixotropy in which when a shear stress having a high shear rate is
applied, the viscosity of the adhesive significantly decreases and
the adhesive flows, and, immediately after the shear stress is
removed, the viscosity recovers. Accordingly, the adhesive produced
by the method for producing an adhesive for a multilayered
heat-recoverable article is easily brought into close contact with
an adherend, and does not easily flow out after the adhesive is
brought into close contact with the adherend.
[0032] The dose of the ionizing radiation absorbed by the resin
composition is preferably 90 kJ/kg or more. By controlling the
absorbed dose of the ionizing radiation to the lower limit or more,
the shear viscosity of the adhesive can be in the above range
easily and reliably, and suitable thixotropy can be imparted to the
adhesive for a multilayered heat-recoverable article.
[0033] The ionizing radiation is preferably an electron beam. By
using an electron beam irradiation apparatus, which is relatively
widely used, production facilities are easily introduced and a
production process can be easily controlled.
[0034] Herein the phrase "does not substantially contain an
inorganic filler" means that an inorganic filler serving as a
viscosity modifier is not contained, and a small amount of an
inorganic material may be contained intentionally or inevitably to
the extent that an effect of adjusting the viscosity is not
exhibited. The term "main component" refers to a component having
the highest content, and, for example, a component having a content
of 50% by mass or more. The term "shear viscosity" refers to a
value measured with a rotational rheometer.
Details of Embodiments of Present Invention
[0035] Embodiments of the present invention will now be described
in detail with reference to the drawings.
[Multilayered Heat-Recoverable Article]
[0036] A multilayered heat-recoverable article 1 illustrated in
FIGS. 1 to 3 is used as a covering for, for example, protection,
insulation, waterproofness, and corrosion prevention of a connected
portion of insulated electric wires, a wiring terminal, a metal
tube, or the like. The multilayered heat-recoverable article 1
includes a cylindrical base material layer 10, and an adhesive
layer 11 formed on an inner circumferential surface of the base
material layer 10.
[Base Material Layer]
[0037] The base material layer 10 is formed as a tube whose
diameter is reduced by heating. The base material layer 10
preferably contains a polyethylene, a polyester, a polyamide, or a
fluororesin. These resins may be used alone or in combination of
two or more resins. When the base material layer 10 contains the
resins exemplified above, the base material layer 10 can have
suitable heat shrinkability. Furthermore, since the resins
exemplified above are available at a low cost, the production cost
can be reduced.
[0038] A flame retardant is preferably added to the base material
layer 10 for the purpose of improving flame retardancy.
Furthermore, other additives may be added to the base material
layer 10, as required. Examples of the additives include an
oxidation inhibitor, a flame retardant, a copper inhibitor, a
lubricant, a colorant, a heat stabilizer, and an ultraviolet
absorber.
<Oxidation Inhibitor>
[0039] Examples of the oxidation inhibitor include phenol-based
compounds, amine-based compounds, hindered amine-based compounds,
hindered phenol-based compounds, salicylic acid derivatives,
benzophenone-based compounds, and benzotriazole-based compounds. In
particular, hindered amine-based compounds, which have a good
effect of suppressing cross-linking, are preferably used. By using
such an oxidation inhibitor, resistance to damage by copper can be
further improved. As the oxidation inhibitor, besides the above
compounds, sulfur-based compounds, phosphorous acid ester-based
compounds, and the like may be used alone or in combination.
[0040] The lower limit of the content of the oxidation inhibitor in
the base material layer 10 is preferably 1 part by mass, and more
preferably 1.5 parts by mass relative to 100 parts by mass of the
resin component. The upper limit of the content of the oxidation
inhibitor is preferably 5 parts by mass, and more preferably 3
parts by mass relative to 100 parts by mass of the resin component.
When the content of the oxidation inhibitor is less than the lower
limit, the base material layer 10 is easily oxidized, and the
multilayered heat-recoverable article 1 may degrade. When the
content of the oxidation inhibitor exceeds the upper limit,
blooming and bleeding may occur.
(Phenol-Based Compound)
[0041] Examples of the phenol-based compounds used as the oxidation
inhibitor include pentaerythritol
tetrakis[3-3,5-di-tert-butyl-4-hydroxyphenyl)propionate],
tetrakis-[methylene-3-(3'5'-di-tert-butyl-4'-hydroxyphenyl)propionate]met-
hane, triethylene
glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate],
and
6-(4-hydroxy-3,5-di-tert-butyl.anilino)-2,4-bis.octyl-thio-1,3,5-triazine-
.
(Amine-Based Compound)
[0042] Examples of the amine-based compounds used as the oxidation
inhibitor include
4,4'-(.alpha.,.alpha.-dimethylbenzyl)diphenylamine, polymerized
products of 2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline,
N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, and
N-isopropyl-N'-phenyl-1,4-phenylenediamine.
<Flame Retardant>
[0043] Examples of the flame retardant include chlorine-based flame
retardants such as chlorinated paraffin, chlorinated polyethylene,
chlorinated polyphenyl, and perchloropentacyclodecane;
bromine-based flame retardants such as
1,2-bis(2,3,4,5,6-pentabromophenyl)ethane,
ethylenebispentabromobenzene, ethylenebispentabromodiphenyl,
tetrabromoethane, tetrabromobisphenol A, hexabromobenzene,
decabromobiphenyl ether, tetrabromophthalic anhydride,
polydibromophenylene oxide, hexabromocyclodecane, and ammonium
bromide; phosphoric acid esters or phosphorus compounds such as
triallyl phosphate, alkyl allyl phosphates, alkyl phosphates,
dimethyl phosphonate, phosphorinate, halogenated phosphorinate
esters, trimethyl phosphate, tributyl phosphate, trioctyl
phosphate, tributoxyethyl phosphate, octyl diphenyl phosphate,
tricresyl phosphate, cresyl phenyl phosphate, triphenyl phosphate,
tris(chloroethyl) phosphate, tris(2-chloropropyl) phosphate,
tris(2,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl)
phosphate, tris(bromochloropropyl) phosphate,
bis(2,3-dibromopropyl) 2,3-dichloropropyl phosphate,
bis(chloropropyl) monooctyl phosphate, polyphosphonate,
polyphosphate, aromatic polyphosphate, dibromoneopentyl glycol, and
aluminum tris(diethylphosphinate); polyols such as phosphonate
polyols, phosphate polyols, and halogen element-containing polyols;
nitrogen compounds such as melamine cyanurate, triazine,
isocyanurates, urea, and guanidine; and other compounds such as
silicone-based polymers, ferrocene, fumaric acid, and maleic acid.
Among these, halogen-based flame retardants such as bromine-based
flame retardants and chlorine-based flame retardants are
preferable. The bromine-based flame retardants and the
chlorine-based flame retardants may be used alone or in combination
of two or more compounds.
[0044] Regarding the range of the content of the flame retardant,
for example, in the case of a bromine-based flame retardant, the
lower limit is preferably 1 part by mass, and more preferably 5
parts by mass relative to 100 parts by mass of the resin component.
The upper limit is preferably 50 parts by mass, and more preferably
40 parts by mass relative to 100 parts by mass of the resin
component. When the content of the flame retardant is less than the
lower limit, the effect of imparting flame retardancy may not be
obtained. When the content of the flame retardant exceeds the upper
limit, toughness and elongation necessary for the heat-recoverable
article may degrade.
<Copper Inhibitor>
[0045] Examples of the copper inhibitor include
3-(N-salicyloyl)amino-1,2,4-triazole, decamethylenedicarboxylic
acid disalicyloylhydrazide, and
2,3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]propionohydrazide.
Damage by copper can be prevented by incorporating the copper
inhibitor in the base material layer 10. In the case where an
oxidation inhibitor is contained in the base material layer 10 and
the adhesive layer 11, the copper inhibitor is not necessarily
contained in the base material layer 10. Thus, by not incorporating
an expensive copper inhibitor, the production cost of the
multilayered heat-recoverable article 1 can be reduced.
[0046] Regarding the range of the content of the copper inhibitor,
for example, in the case where the copper inhibitor is
3-(N-salicyloyl)amino-1,2,4-triazole, the lower limit is preferably
0.5 parts by mass, and more preferably 1 part by mass relative to
100 parts by mass of the resin component. The upper limit is
preferably 10 parts by mass, and more preferably 5 parts by mass
relative to 100 parts by mass of the resin component. When the
content of the copper inhibitor is less than the lower limit, the
effect of the copper inhibitor may not be obtained. Even when the
content of the copper inhibitor exceeds the upper limit, an
improvement in the effect of preventing damage by copper is not
obtained.
[Adhesive Layer]
[0047] The adhesive layer 11 is a layer for enhancing adhesiveness
between a portion to be adhered and the base material layer 10 and
improving a waterproofing property, etc. The adhesive layer 11 is
formed of a resin composition that contains a polyimide as a main
component and that does not substantially contain an inorganic
filler. The adhesive layer 11 is cross-linked by irradiation with
ionizing radiation. The resin composition that forms the adhesive
layer 11 preferably contains an oxidation inhibitor. The resin
composition that forms the adhesive layer 11 may contain a very
low-density polyethylene or an ethylene copolymer. Furthermore,
other additives may be added to the resin composition that forms
the adhesive layer 11, as required. Examples of the additives
include an oxidation inhibitor, a copper inhibitor, a viscosity
improver, a deterioration inhibitor, a flame retardant, a
lubricant, a colorant, a heat stabilizer, an ultraviolet absorber,
and a tackifier.
[0048] The lower limit of a shear viscosity of the adhesive layer
11 at 150.degree. C. at a shear rate of 0.01 s.sup.-1 is preferably
300 Pas, and more preferably 400 Pas. The upper limit of the shear
viscosity at a shear rate of 0.01 s.sup.-1 is preferably 3,000 Pas,
and more preferably 1,000 Pas. When the shear viscosity at a shear
rate of 0.01 s.sup.-1 is less than the lower limit, the adhesive
layer 11 may flow out from the base material layer 10, or it may
become difficult to stably extrude the adhesive layer 11. When the
shear viscosity at a shear rate of 0.01 s.sup.-1 exceeds the upper
limit, extrusion moldability may be insufficient.
[0049] The lower limit of a shear viscosity of the adhesive layer
11 at 150.degree. C. at a shear rate of 100 s.sup.-1 is preferably
10 Pas, and more preferably 20 Pas. The upper limit of the shear
viscosity of the adhesive layer 11 at 150.degree. C. at a shear
rate of 100 s.sup.-1 is preferably 200 Pas, and more preferably 100
Pas. When the shear viscosity at a shear rate of 100 s.sup.-1 is
less than the lower limit, during heat shrinkage of the base
material layer 10, the adhesive layer 11 may excessively flow and
may flow out from the base material layer 10. When the shear
viscosity at a shear rate of 100 exceeds the upper limit, during
heat shrinkage of the base material layer 10, the adhesive layer 11
cannot deform sufficiently and the adhesion of the multilayered
heat-recoverable article 1 to an adherend may be insufficient.
<Polyamide>
[0050] In the resin composition that forms the adhesive layer 11,
at least a polyamide which is a main component is cross-linked by
irradiation with ionizing radiation. The cross-linked polyamide
forms a network and imparts the adhesive layer 11 with thixotropy
in which the shear viscosity decreases when the shear rate is high,
as described above.
[0051] In the case where a trimer acid content is increased in the
synthesis of a polyamide, the proportion of the synthesized
polyamide having a branched structure increases. A polyamide having
a high proportion of a branched structure is easily slightly
cross-linked. Accordingly, such a polyamide is easily cross-linked
by irradiation with ionizing radiation, and an improvement in
thixotropy of the adhesive layer increases. In the case where a
resin composition containing only a polyamide is used, the trimer
acid content of the polyamide is preferably 20% by mass or more,
more preferably 25% by mass or more, and still more preferably 30%
by mass or more. When the trimer acid content of the polyamide is
less than 20% by mass, the polyamide is preferably used in
combination with another resin such as a very low-density
polyethylene or an ethylene copolymer.
[0052] The lower limit of a melt flow rate (MFR) of a raw material
polyamide before being irradiated with ionizing radiation is
preferably 15 g/10 min, more preferably 50 g/10 min, and still more
preferably 100 g/10 min. The upper limit of the MFR of the raw
material polyamide is preferably 1,000 g/10 min, more preferably
500 g/10 min, and still more preferably 300 g/10 min.
[0053] When the MFR of the raw material polyamide is less than the
lower limit, flowability is excessively high even after
cross-linking. Accordingly, the adhesive layer 11 may flow out from
the base material layer 10, or it may become difficult to stably
extrude the adhesive layer 11. In the case where the MFR of the raw
material polyamide exceeds the upper limit, flowability of the
adhesive layer 11 during heat shrinkage of the base material layer
10 is insufficient when the multilayered heat-recoverable article 1
is used. Consequently, adhesion of the multilayered
heat-recoverable article 1 to an adherend may be insufficient.
Herein, the MFR is an index that represents flowability of a resin.
The term "MFR" refers to a value measured using an extrusion
plastometer specified in JIS-K6760 (1997). Regarding polyamides,
the MFR is a value measured at a temperature of 120.degree. C. and
at a load of 2.16 kg. Regarding other resins, the MFR is a value
measured at a temperature of 190.degree. C. and at a load of 2.16
kg.
<Very Low-Density Polyethylene>
[0054] The resin composition that forms the adhesive layer 11 may
contain a very low-density polyethylene (VLDPE) as a resin
component for the purpose of improving thixotropy obtained by the
cross-linking. The very low-density polyethylene is a polyethylene
having a specific gravity of 0.91 g/cm.sup.3 or less.
[0055] The lower limit of the content of the very low-density
polyethylene in the resin composition that forms the adhesive layer
11 is preferably 20% by mass, and more preferably 25% by mass. The
upper limit of the content of the very low-density polyethylene is
preferably 49% by mass, and more preferably 45% by mass.
[0056] When the content of the very low-density polyethylene is
less than the lower limit, the effect of improving thixotropy of
the adhesive layer 11 may be insufficient. When the content of the
very low-density polyethylene exceeds the upper limit, the adhesive
layer 11 has an excessively high viscosity, and adhesion of the
multilayered heat-recoverable article 1 to an adherend may be
insufficient.
[0057] The lower limit of the MFR of the very low-density
polyethylene is preferably 0.1 g/10 min, and more preferably 1 g/10
min. The upper limit of the MFR of the very low-density
polyethylene is preferably 800 g/10 min, and more preferably 400
g/10 g. When the MFR of the very low-density polyethylene is less
than the lower limit, flowability of the resin composition during
heating may be insufficient. When the MFR of the very low-density
polyethylene exceeds the upper limit, the viscosity of the resin
composition tends to be low, and a large absorbed dose of ionizing
radiation may be necessary, which may be uneconomical.
[0058] The lower limit of the specific gravity of the very
low-density polyethylene is preferably 0.85 g/cm.sup.3, and more
preferably 0.87 g/cm.sup.3. The upper limit of the specific gravity
of the very low-density polyethylene is preferably 0.91 g/cm.sup.3,
more preferably 0.90 g/cm.sup.3, and still more preferably 0.89
g/cm.sup.3. A very low-density polyethylene having a low specific
gravity has a small amount of crystal and is easily cross-linked,
and thus easily forms a long-chain branched structure. Accordingly,
an improvement in thixotropy of the adhesive layer increases. When
the specific gravity of the very low-density polyethylene is less
than the lower limit, the viscosity of the resin composition tends
to be low, and a large absorbed dose of ionizing radiation may be
necessary, which may be uneconomical. When the specific gravity of
the very low-density polyethylene exceeds the upper limit,
flowability of the resin composition during heating may be
insufficient.
[0059] In the case where the resin composition that forms the
adhesive layer 11 contains a very low-density polyethylene, the
resin composition may contain, as an additive, an alloying agent
for enhancing compatibility between the polyamide and the very
low-density polyethylene. Examples of the alloying agent include
maleic anhydride and acrylic acid-modified polyethylene. The
content of the alloying agent in the resin composition that forms
the adhesive layer 11 may be 0.5% by mass or more and 5% by mass or
less.
<Ethylene Copolymer>
[0060] The resin composition that forms the adhesive layer 11 may
contain an ethylene copolymer as a resin component for the purpose
of improving thixotropy obtained by the cross-linking. Specific
examples of the ethylene copolymer include ethylene-vinyl acetate
copolymers (EVA), ethylene-butene copolymers (EBA), ethylene-octene
copolymers, ethylene-ethyl acrylate copolymers, and ethylene-butyl
acrylate copolymers. The ethylene copolymer is particularly
preferably an ethylene-vinyl acetate copolymer.
[0061] The lower limit of the content of the ethylene copolymer in
the resin composition that forms the adhesive layer 11 is
preferably 20% by mass, and more preferably 25% by mass. The upper
limit of the content of the ethylene copolymer is 49% by mass, and
more preferably 45% by mass. When the content of the ethylene
copolymer is less than the lower limit, the effect of improving
thixotropy of the adhesive layer 11 may be insufficient. When the
content of the ethylene copolymer exceeds the upper limit, the
adhesive layer 11 has an excessively high viscosity, and adhesion
of the multilayered heat-recoverable article 1 to an adherend may
be insufficient.
<Ethylene-Vinyl Acetate Copolymer>
[0062] The lower limit of the MFR of an ethylene-vinyl acetate
copolymer, which is particularly preferable among the ethylene
copolymers mentioned above, is preferably 1 g/10 min, and more
preferably 5 g/10 min. The upper limit of the MFR of the ethylene
vinyl acetate copolymer is preferably 2,000 g/10 min, more
preferably 1,000 g/10 min, and still more preferably 500 g/10 min.
When the MFR of the ethylene-vinyl acetate copolymer is less than
the lower limit, flowability of the resin composition during
heating may be insufficient. When the MFR of the ethylene-vinyl
acetate copolymer exceeds the upper limit, the viscosity of the
resin composition tends to be low, and a large absorbed dose of
ionizing radiation may be necessary, which may be uneconomical.
<Oxidation Inhibitor>
[0063] The same oxidation inhibitor as that in the base material
layer 10 may be used as the oxidation inhibitor in the adhesive
layer 11.
[0064] The oxidation inhibitor also has a function of suppressing
cross-linking of the resin composition caused by irradiation with
ionizing radiation. The lower limit of the content of the oxidation
inhibitor in the adhesive layer 11 is preferably 1 part by mass,
and more preferably 2 parts by mass relative to 100 parts by mass
of the resin component in the resin composition. The upper limit of
the content of the oxidation inhibitor is preferably 20 parts by
mass, and more preferably 15 parts by mass relative to 100 parts by
mass of the resin component in the resin composition. When the
content of the oxidation inhibitor is less than the lower limit,
the adhesive layer 11 and the base material layer 10 are easily
oxidized, and the multilayered heat-recoverable article 1 may
degrade. In addition, it may become difficult to uniformly
cross-link the material to a deep position as a result of
irradiation with ionizing radiation.
[0065] Even when the content of the oxidation inhibitor exceeds the
upper limit, an improvement in the effect of preventing the
adhesive layer 11 and the base material layer 10 from being
oxidized is not obtained, and imparting of thixotropy due to
cross-linking may be inhibited.
<Copper Inhibitor>
[0066] Examples of the copper inhibitor include compounds the same
as those used as the copper inhibitor in the base material layer
10. In the case where an oxidation inhibitor is contained in the
base material layer 10 and the adhesive layer 11, the copper
inhibitor is not necessarily contained in the adhesive layer
11.
<Deterioration Inhibitor>
[0067] The deterioration inhibitor is an agent for suppressing
deterioration of an adherend to which the multilayered
heat-recoverable article 1 adheres. Typically, the deterioration
inhibitor is an agent for suppressing generation of cracks of an
insulating layer of an insulated electric wire due to a basic
component contained in the insulating layer or the adhesive layer
11 of the multilayered heat-recoverable article 1. This
deterioration inhibitor can also function as a viscosity improver.
The deterioration inhibitor is selected in accordance with the
factor of deterioration of an adherend. For example, in the case
where deterioration of an adherend due to a basic component is
suppressed, it is possible to use a compound that suppresses the
occurrence of a dehydrochlorination reaction due to a basic
component or a compound that can capture or neutralize hydrogen
chloride, a chloride ion, and the like generated by a hydrochloric
acid reaction. Examples of the deterioration inhibitor include
activated clay, hydrotalcite, and oxidation inhibitors (acid value:
10 mgKOH/g or more) containing phosphorus. By incorporating any of
these deterioration inhibitors in the adhesive layer 11,
deterioration of an adherend due to a basic component in the
adhesive layer 11 can be suppressed by, for example, adsorbing a
nitrogen-containing compound, incorporating an anion, and capturing
hydrogen chloride generated by a dehydrochlorination reaction.
<Method for Producing Multilayered Heat-Recoverable
Article>
[0068] The multilayered heat-recoverable article 1 can be produced
by, for example, the steps described below.
(1) A step of preparing a base material layer resin composition for
forming a base material layer 10 (2) A step of producing an
adhesive resin composition for forming an adhesive layer 11 (3) A
step of forming a multilayered extrusion-molded product by
extruding the base material layer resin composition and the
adhesive resin composition using a melt-extruder (4) A step of
expanding a diameter of the multilayered extrusion-molded product
to obtain a multilayered heat-recoverable article 1
(1) Base Material Layer Resin Composition Preparation Step
[0069] A base material layer resin composition can be prepared by
mixing a resin component, and, as required, an additive using, for
example, a melt-mixer. A known melt-mixer, for example, an open
roll mill, a Banbury mixer, a pressure kneader, a single-screw
mixer, or a multi-screw mixer may be used.
(2) Adhesive Production Step
[0070] An adhesive production step includes a step of preparing an
adhesive resin composition and a step of irradiating the adhesive
resin composition with ionizing radiation.
(Adhesive Resin Composition Preparation Step)
[0071] An adhesive resin composition contains a polyamide as a main
component. The adhesive resin composition may contain, as a resin
component, a very low-density polyethylene or an ethylene copolymer
in addition to the polyamide. The adhesive resin composition can be
prepared by mixing the resin component, an oxidation inhibitor,
and, as required, an additive using, for example, a melt-mixer. The
same melt-mixer as that used in the preparation of the base
material layer resin composition can be used as the melt-mixer.
(Ionizing Radiation Irradiation Step)
[0072] Examples of ionizing radiation applied to the adhesive resin
composition include electron beams and gamma rays. Electron beams,
for which irradiation equipment is relatively easily prepared, are
preferable.
[0073] In this ionizing radiation irradiation step, a dose of the
ionizing radiation is controlled so that a shear viscosity of the
resulting adhesive at 150.degree. C. is 300 Pas or more at a shear
rate of 0.01 s.sup.-1 and 200 Pas or less at a shear rate of 100
s.sup.-1.
[0074] In order to specifically achieve the above shear viscosity,
the lower limit of the dose of the ionizing radiation absorbed by
the adhesive resin composition is preferably 90 kJ/kg, and more
preferably 200 kJ/kg. The upper limit of the dose of the ionizing
radiation absorbed by the adhesive resin composition is preferably
1,000 kJ/kg, and more preferably 500 kJ/kg. When the dose of the
ionizing radiation absorbed by the adhesive resin composition is
less than the lower limit, sufficient thixotropy may not be
imparted to the adhesive resin composition. When the dose of the
ionizing radiation absorbed by the adhesive resin composition
exceeds the upper limit, the cost may be unnecessarily increased,
or the viscosity may be excessively increased by excessive
cross-linking of the resin composition, which may result in the
difficulty in injection molding.
[0075] The ionizing radiation irradiation step may be performed,
prior to the adhesive resin composition preparation step, on a
resin composition prepared by mixing an oxidation inhibitor with a
resin component that contains at least a polyamide and that may
contain a very low-density polyethylene or an ethylene copolymer,
the resin component being contained in the adhesive resin
composition. That is, a resin other than the above resin component
and an additive other than the oxidation inhibitor may be added
after the irradiation with ionizing radiation.
(3) Multilayered Extrusion-Molded Product Formation Step
[0076] A multilayered extrusion-molded product is formed by
simultaneously extruding the base material layer resin composition
and the adhesive resin composition using a known melt-extruder. As
a result, the multilayered extrusion-molded product is formed as a
molded product in which an inner layer corresponding to the
adhesive layer 11 is formed on an inner circumferential surface of
an outer layer corresponding to the base material layer 10. Heat
resistance of the multilayered extrusion-molded product may be
improved by cross-linking the material constituting the base
material layer resin composition. Examples of the cross-linking
method include cross-linking by irradiation with ionizing
radiation, chemical cross-linking, and thermal cross-linking.
[0077] The dimensions of the multilayered extrusion-molded product
can be designed in accordance with the use etc. Regarding the
dimensions of the base material layer 10 of the multilayered
extrusion-molded product, for example, the inner diameter and the
wall thickness are 1.0 to 30 mm and 0.1 to 10 mm, respectively.
Regarding the dimensions of the adhesive layer 11 of the
multilayered extrusion-molded product, for example, the inner
diameter and the wall thickness are 0.1 to 10 mm and 0.1 mm to 8.5
mm, respectively.
(4) Diameter Expansion Step of Multilayered Extrusion-Molded
Product
[0078] Expansion of the diameter of the multilayered
extrusion-molded product is performed as follows. The multilayered
extrusion-molded product is inflated so as to have a predetermined
inner diameter by, for example, introducing compressed air to the
inside thereof in a state where the multilayered extrusion-molded
product is heated at a temperature equal to or higher than a
melting point thereof. Subsequently, the resulting multilayered
extrusion-molded product is cooled to fix the shape. Such an
expansion of the diameter of the multilayered extrusion-molded
product is performed such that, for example, the inner diameter of
the multilayered extrusion-molded product is increased by about 2
to 4 times. The resulting product obtained by expanding the
diameter of the multilayered extrusion-molded product and fixing
the shape as described above is the multilayered heat-recoverable
article 1.
[Advantages]
[0079] According to the multilayered heat-recoverable article 1,
since the adhesive layer 11 contains a polyamide cross-liked by
irradiation with ionizing radiation, the adhesive layer 11 does not
flow before and after heat shrinkage of the base material layer 10,
and exhibits sufficient flowability during heat shrinkage of the
base material layer 10 and can closely adhere to an adherend.
[Wire Splice and Wire Harness]
[0080] The multilayered heat-recoverable article 1 can be used for,
for example, protection, insulation, waterproofness, and corrosion
prevention of wires such as a polyethylene (PE) electric wire or PE
cable that includes an insulating layer composed of PE, the
insulating layer covering a conductor, and a polyvinyl chloride
(PVC) electric wire or PVC cable that includes an insulating layer
composed of PVC. Specifically, the multilayered heat-recoverable
article 1 can be applied to a wire splice and a wire harness.
[0081] FIG. 4 illustrates an example in which the multilayered
heat-recoverable article 1 is applied to a wire splice. FIGS. 5 and
6 illustrate an example in which the multilayered heat-recoverable
article 1 is applied to a wire harness.
[0082] The wire splice illustrated in FIG. 4 is obtained by
stranding conductor wires 21 of a pair of wires 20 to connect to
each other, and allowing a tube 1a to adhere to the connected
portion, the tube 1a being formed by thermally shrinking the
multilayered heat-recoverable article 1 in FIG. 1.
[0083] Each of the wires 20 is a cable or an insulated electric
wire such as a PE electric wire or a PVC electric wire. For
example, a wire that includes an insulating layer serving as an
outermost layer and containing polyvinyl chloride as a main
component is used as the wire 20. The content of polyvinyl chloride
in the insulating layer is, for example, 50% by mass or more and
95% by mass or less. In this wire splice, the tube 1a can
contribute to, for example, protection, insulation, waterproofness,
and corrosion prevention of the connected portion.
[0084] The wire harness illustrated in FIGS. 5 and 6 is obtained by
bundling a plurality of wires 30 with a tube 1a formed by thermally
shrinking the multilayered heat-recoverable article 1 in FIG. 1,
and providing a multi-pin connector 31 at an end of the wires 30.
The wires 30 are the same as the wires 20 of the wire splice
illustrated in FIG. 4. In this wire harness, the tube 1a has not
only a function of bundling the wires 30 but also a function of
protecting each of the wires 30, etc.
[0085] It should be noted that the wire splice and the wire harness
of the present invention may not be exactly discriminated from each
other. There may be a case where a wire splice also functions as a
wire harness.
Other Embodiments
[0086] It is to be understood that the embodiments disclosed herein
are only illustrative and are not restrictive in all respects. The
scope of the present invention is not limited to the configurations
of the above embodiments but is defined by the claims described
below. It is intended that the scope of the present invention
includes equivalents of the claims and all modifications within the
scope of the claims.
[0087] The multilayered heat-recoverable article of the present
invention is not limited to the multilayered heat-recoverable
article 1 illustrated in FIGS. 1 to 3, the multilayered
heat-recoverable article 1 including a base material layer 10
formed so as to have a tubular shape. Alternatively, for example,
the multilayered heat-recoverable article may be a multilayered
heat-recoverable article 1A including a base material layer 10A
formed so as to have a cap shape, as illustrated in FIG. 7. This
multilayered heat-recoverable article 1A is obtained by thermally
shrinking an end of the multilayered heat-recoverable article 1 to
close the end. As a result, an adhesive layer 11A is disposed on an
inner circumferential surface of the cap-shaped base material layer
10A. This multilayered heat-recoverable article 1A can be suitably
used for, for example, a terminal treatment of wiring.
[0088] The multilayered heat-recoverable article of the present
invention may be formed by separately extruding a base material
layer and an adhesive layer. The multilayered heat-recoverable
article in this case is used by arranging an adhesive layer on an
inner circumferential surface of a base material layer that has
been inflated after extrusion molding, covering an adherend with
the base material layer having the adhesive layer on an inner
circumferential surface thereof, and shrinking the base material
layer.
[0089] The wire splice of the present invention is not particularly
limited as long as a multilayered heat-recoverable article adheres
to a connected portion of wires. In the wire splice, a single wire
may be connected to a plurality of wires, a plurality of wires may
be connected to a plurality of wires, or ends of a plurality of
wires may be integrally connected to each other, as in a terminal
treatment of wiring. Alternatively, the wire splice of the present
invention may have other forms.
[0090] The wire harness of the present invention may be constituted
as a so-called flat harness in which a plurality of wires are
bundled in a planar shape. Alternatively, the wire harness of the
present invention may have other forms.
Examples
[0091] The present invention will now be described in more detail
on the basis of Examples. However, the Examples do not limit the
scope of the present invention.
[0092] Adhesive resin composition Nos. 1 to 11 were experimentally
prepared so as to have the compositions shown in Table I using, as
resin raw materials, a polyamide (1), very low-density
polyethylenes, and ethylene-vinyl acetate copolymers. In Table I,
the symbol "-" means that the component is not mixed.
TABLE-US-00001 TABLE I Component Adhesive resin composition (parts
by mass) No. No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10
No. 11 Polyamide (1) 70 55 70 70 70 100 85 40 70 85 -- VLDPE (A) 30
45 -- -- -- -- 15 60 -- -- -- VLDPE (B) -- -- 30 -- -- -- -- -- --
-- -- EVA (A) -- -- -- -- -- -- -- -- 30 -- -- EVA (B) -- -- -- 30
-- -- -- -- -- 15 -- EVA (C) -- -- -- -- 30 -- -- -- -- -- 100
Inorganic filler -- -- -- -- -- -- -- -- -- -- 10
[0093] A polyamide containing a trimer acid in an amount of 14% by
mass and having an MFR of 120 g/10 min and a softening point of
105.degree. C. was used as the raw material polyamide (1). A very
low-density polyethylene (VLDPE) (A) having an MFR of 30 g/10 min,
a melting point of 96.degree. C., and a specific gravity of 0.90
g/cm.sup.3, and a VLDPE (B) having an MFR of 3 g/10 min, a melting
point of 97.degree. C., and a specific gravity of 0.90 g/cm.sup.3
were used as the very low-density polyethylenes. An ethylene-vinyl
acetate copolymer (EVA) (A) having an MFR of 800 g/10 min, a
melting point of 73.degree. C., a specific gravity of 0.95
g/cm.sup.3, and a vinyl acetate content of 28% by mass, an EVA (B)
having an MFR of 400 g/10 min, a melting point of 62.degree. C., a
specific gravity of 0.95 g/cm.sup.3, and a vinyl acetate content of
28% by mass, and an EVA (C) having an MFR of 150 g/10 min, a
melting point of 65.degree. C., a specific gravity of 0.95
g/cm.sup.3, and a vinyl acetate content of 28% by mass were used as
the ethylene-vinyl acetate copolymers.
[0094] In each of the adhesive resin composition Nos. 1 to 11, 10
parts by mass of an oxidation inhibitor was added relative to 100
parts by mass of the resin component. Furthermore, in the adhesive
of No. 11, 10 parts by mass of hydrophilic fumed silica ("AEROSIL
200" manufactured by Nippon Aerosil Co., Ltd.) having a specific
surface area of 200 m.sup.2/g was added as an inorganic filler for
adjusting the viscosity relative to 100 parts by mass of the resin
component.
[0095] The resin component and the additives were sufficiently
mixed to prepare the adhesive resin compositions. Each of the
adhesive resin compositions was irradiated with an electron beam so
that the absorbed dose was different. Thus, a plurality of
adhesives were obtained from each of the adhesive resin
compositions. The absorbed dose of the electron beam was adjusted
to 100 kJ/kg, 200 kJ/kg, 300 kJ/kg, 400 kJ/kg, and 500 kJ/kg.
[0096] For each of the adhesives that were prepared by irradiating
the adhesive resin composition Nos. 1 to 11 with an electron beam
and that had different absorbed doses, a shear viscosity was
measured in order to examine the ease of flowing of the adhesive
from a base material layer after heat shrinkage when the adhesive
was used as an adhesive for a multilayered heat-recoverable
article.
(Measurement of Shear Viscosity)
[0097] The shear viscosity was measured at a temperature of
150.degree. C. using a rotational rheometer ("MCR302" manufactured
by Anton Paar) with a PP-12 jig. The shear viscosity was measured
while the shear rate was changed from 0.001 s.sup.-1 to 1,000
s.sup.-1. The shear rate is determined by the shape of a rotator
and the rotational speed. The rotational rheometer is configured to
automatically determine the shear rate.
[0098] Table II shows a shear viscosity of each of the adhesives at
a shear rate of 0.01 s.sup.-1. Table III shows a shear viscosity of
each of the adhesives at a shear rate of 100 s.sup.-1. In Tables
below, the symbol "-" means that the measurement could not be
performed or a measurement value or an evaluation value was not
obtained for some other reasons.
TABLE-US-00002 TABLE II Shear viscosity (Pa s) Adhesive resin
composition (Shear rate: 0.01 s.sup.-1) No. 1 No. 2 No. 3 No. 4 No.
5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 Absorbed 100 (kJ/kg) 140
270 320 80 120 40 80 980 60 40 -- dose 200 (kJ/kg) 150 790 1870 90
130 30 110 6530 60 50 -- 300 (kJ/kg) 760 5180 1350 120 180 40 240
9830 90 70 580 400 (kJ/kg) 740 8150 3520 150 550 50 480 -- 80 70 --
500 (kJ/kg) 1050 9220 5380 380 450 70 510 -- 100 100 --
TABLE-US-00003 TABLE III Shear viscosity (Pa s) Adhesive resin
composition (Shear rate: 100 s.sup.-1) No. 1 No. 2 No. 3 No. 4 No.
5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 Absorbed 100 (kJ/kg) 30 80
70 40 40 20 50 350 30 30 -- dose 200 (kJ/kg) 40 90 90 50 40 30 50
3800 40 40 -- 300 (kJ/kg) 40 140 90 50 50 20 70 7540 40 40 180 400
(kJ/kg) 60 210 140 60 80 30 70 -- 50 50 -- 500 (kJ/kg) 60 300 220
70 70 30 80 -- 40 50 --
[0099] As shown above, regarding the adhesive resin composition No.
1, when the absorbed dose of the electron beam was 300 kJ/kg or
more and 500 kJ/kg or less, the shear viscosity at a shear rate of
0.01 s.sup.-1 was 300 Pas or more, and the shear viscosity at a
shear rate of 100 s.sup.-1 was 200 Pas or less. Thus, the adhesive
resin composition had thixotropy suitable for an adhesive for a
multilayered heat-recoverable article.
[0100] Similarly, regarding the adhesive resin composition No. 2,
when the absorbed dose of the electron beam was 200 kJ/kg or more
and 300 kJ/kg or less; regarding the adhesive resin composition No.
3, when the absorbed dose of the electron beam was 100 kJ/kg or
more and 400 kJ/kg or less; regarding the adhesive resin
composition No. 4, when the absorbed dose of the electron beam was
500 kJ/kg; regarding the adhesive resin composition No. 5, when the
absorbed dose of the electron beam was 400 kJ/kg or more and 500
kJ/kg or less; regarding the adhesive resin composition No. 7, when
the absorbed dose of the electron beam was 400 kJ/kg or more and
500 kJ/kg or less; and regarding the adhesive resin composition No.
11, when the absorbed dose of the electron beam was 300 kJ/kg, the
adhesive resin composition had thixotropy suitable for an adhesive
for a multilayered heat-recoverable article.
[0101] In contrast, the adhesive resin composition No. 6 and Nos. 8
to 10 did not have thixotropy suitable for adhesives for
multilayered heat-recoverable articles within this range of the
absorbed dose of the electron beam.
[0102] Furthermore, among these, regarding a plurality of adhesives
formed by irradiating the adhesive resin composition Nos. 1 and 6
with an electron beam such that the absorbed dose was different,
the shear viscosity was measured under the conditions similar to
those in Tables II and III. FIGS. 9 and 10 each show the detailed
relationship between the shear rate and the shear viscosity
obtained by this measurement.
[0103] As shown in the figure, regarding the adhesive resin
composition No. 1, before the electron beam irradiation, a change
in the shear viscosity with the change in the shear rate is small.
However, the adhesive resin composition is modified by the electron
beam irradiation, and the shear viscosity in a low shear rate
region is sufficiently higher than the shear viscosity in a high
shear rate region. Thus, the adhesive resin composition No. 1 can
be used as an adhesive which has suitable thixotropy and which does
not easily flow out from a base material layer after heat shrinkage
of a multilayered heat-recoverable article.
[0104] In contrast, regarding the adhesive resin composition No. 6,
in the case of a shear rate of 100 s.sup.-1, preferable results
were obtained when the absorbed dose of the electron beam was 500
kJ/kg or less. However, in the case of a shear rate of 0.01
s.sup.-1, the shear viscosity was 300 Pas or less. Thus, the
adhesive resin composition No. 6 could not be used as an adhesive
having suitable thixotropy.
[0105] Furthermore, regarding an adhesive prepared by irradiating
the adhesive resin composition No. 1 with an electron beam such
that the absorbed dose became 500 kJ/kg, immediately after the
shear viscosity was measured once by the same method for measuring
a shear viscosity as that shown in Tables II and III, the shear
viscosity was again measured in order to verify the recovery force
of the shear viscosity. FIG. 11 shows the measurement results. As
shown in the figure, the first measurement results of the shear
viscosity of this adhesive are not significantly different from the
second measurement results of the shear viscosity of this adhesive.
Accordingly, it is evaluated that, even after this adhesive is
subjected to a shear once, the shear viscosity recovers immediately
after the shear stress is removed.
[0106] Next, for each of the adhesives that were prepared by
irradiating the adhesive resin composition Nos. 1 to 11 with an
electron beam and that had different absorbed doses, a dripping
property test described below was conducted.
(Dripping Property Test)
[0107] The dripping property test is conducted as follows. First, a
sheet-like adhesive having a thickness of 1 mm is cut to have
dimensions of 5 mm.times.40 mm, and the mass of the sheet-like
adhesive is measured. The resulting sheet-like adhesive A obtained
by cutting is supported from four directions using four glass
plates P, as illustrated in FIG. 8. Next, this sample is held in a
thermostatic chamber at 150.degree. C. in midair in the vertical
direction and is left to stand for 24 hours. Subsequently, whether
or not the adhesive A drips from the glass plates is examined.
After further 72 hours, that is, after the sample is left to stand
for total 96 hours, the mass of the adhesive A that has dripped
from the glass plates is measured, and a dripping ratio (a ratio of
the mass of the dripped adhesive to the mass of the original
sheet-like adhesive) is calculated.
[0108] Table IV shows the dripping ratio of each of the
adhesives.
TABLE-US-00004 TABLE IV Dripping ratio Adhesive resin composition
(mass %) No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No.
10 No. 11 Absorbed 100 (kJ/kg) 80 0 0 70 70 70 80 0 70 80 -- dose
200 (kJ/kg) 70 0 0 80 70 70 80 0 80 70 -- 300 (kJ/kg) 0 0 0 70 80
70 70 0 70 70 60 400 (kJ/kg) 0 0 0 50 0 70 70 -- 70 70 -- 500
(kJ/kg) 0 0 0 0 0 60 60 -- 70 50 --
[0109] Table V shows the results of a dripping property evaluated
in consideration of the occurrence or nonoccurrence of dripping
after 24 hours in the dripping property test. In the evaluation of
the dripping property, when the dripping ratio was 0% in the
dripping property test, the sample is evaluated as "A". When
dripping occurred after 24 hours, the sample is evaluated as "B".
When dripping did not occur after 24 hours and occurred after 96
hours, the sample is evaluated as "C".
TABLE-US-00005 TABLE V Dripping property Adhesive resin composition
evaluation No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9
No. 10 No. 11 Absorbed 100 (kJ/kg) B A A B B B B A B B -- dose 200
(kJ/kg) B A A B B B B A B B -- 300 (kJ/kg) A A A B B B B A B B C
400 (kJ/kg) A A A B A B B -- B B -- 500 (kJ/kg) A A A A A B B -- B
B --
[0110] As shown above, regarding the adhesive resin composition No.
1, when the absorbed dose of the electron beam is 300 kJ/kg or more
and 500 kJ/kg or less, the dripping ratio after 96 hours is 0%.
Accordingly, it is evaluated that, even in a multilayered
heat-recoverable article, the adhesive does not easily flow out
from a base material layer.
[0111] Similarly, regarding the adhesive resin composition Nos. 2
and 3, when the absorbed dose of the electron beam is 100 kJ/kg or
more and 500 kJ/kg or less; regarding the adhesive resin
composition No. 4, when the absorbed dose of the electron beam is
500 kJ/kg; regarding the adhesive resin composition No. 5, when the
absorbed dose of the electron beam is 400 kJ/kg or more and 500
kJ/kg or less; and regarding the adhesive resin composition No. 8,
when the absorbed dose of the electron beam is 100 kJ/kg or more
and 300 kJ/kg or less, it is evaluated that when the adhesive resin
composition is used as an adhesive for a multilayered
heat-recoverable article, the adhesive does not easily flow out
from a base material layer after heat shrinkage.
[0112] In contrast, the adhesive resin composition No. 6, No. 7,
and Nos. 9 to 11 did not have dripping properties suitable for
adhesives for multilayered heat-recoverable articles within this
range.
[0113] Furthermore, for each of the adhesives prepared by
irradiating the adhesive resin composition Nos. 1 to 11 with an
electron beam, waterproofing properties in multilayered
heat-recoverable articles were evaluated by a waterproof test
described below.
(Waterproof Test)
[0114] The waterproof test was conducted as follows. A wire splice
prepared by using a multilayered heat-recoverable article using
each of the adhesives was put in water. Air at 200 kPa was blown
for 30 seconds from an end from which one PVC electric wire in the
multilayered heat-recoverable article extended. Whether or not
bubbles were generated from another end from which four PVC
electric wires extended was examined. In the waterproof test, when
bubbles were not generated, the sample was evaluated as "A". When
bubbles were generated, the sample was evaluated as "B".
[0115] The wire splice used in the waterproof test was prepared as
follows. One PVC electric wire was connected to four PVC electric
wires by welding conductor wires thereof, and the welded portion
was covered with a multilayered heat-recoverable article. In this
state, the resulting electric wires were horizontally placed on a
floor of a thermostatic chamber at 180.degree. C., and heated for
90 seconds to shrink a base material layer. In the wire splice
prepared as described above, one PVC electric wire extends from an
end of a multilayered heat-recoverable article, and four PVC
electric wires extend from another end of the multilayered
heat-recoverable article.
[0116] Table VI shows evaluation results of waterproofing
properties of the adhesives determined by the waterproof test.
TABLE-US-00006 TABLE VI Waterproofing property Adhesive resin
composition evaluation No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7
No. 8 No. 9 No. 10 No. 11 Absorbed 100 (kJ/kg) A A A A A A A B A A
-- dose 200 (kJ/kg) A A A A A A A B A A -- 300 (kJ/kg) A A A A A A
A B A A A 400 (kJ/kg) A B A A A A A -- A A -- 500 (kJ/kg) A B B A A
A A -- A A --
[0117] As shown above, regarding the adhesive resin composition No.
1, Nos. 4 to 7, No. 9, and No. 10, when the absorbed dose of the
electron beam was 100 kJ/kg or more and 500 kJ/kg or less;
regarding the adhesive resin composition No. 2, when the absorbed
dose of the electron beam was 100 kJ/kg or more and 300 kJ/kg or
less; regarding the adhesive resin composition No. 3, when the
absorbed dose of the electron beam was 100 kJ/kg or more and 400
kJ/kg or less; and regarding the adhesive resin composition No. 11,
when the absorbed dose of the electron beam was 300 kJ/kg, the
adhesive had a good waterproofing property. In contrast, the
adhesive resin composition No. 8 did not have a good waterproofing
property in any of the cases.
[0118] Next, adhesive resin composition Nos. 12 to 14 were
experimentally prepared so as to have the compositions shown in
Table VII using, as resin raw materials, the polyamide (1) used in
the adhesive resin composition Nos. 1 to 10, a polyamide (2)
different from the polyamide (1), and a very low-density
polyethylene. In Table VII, the symbol "-" means that the component
is not mixed.
TABLE-US-00007 TABLE VII Component Adhesive resin composition
(parts by mass) No. 12 No. 13 No. 14 Polyamide (1) -- 70 --
Polyamide (2) 100 -- 70 VLDPE (C) -- 30 30
[0119] A polyamide containing a trimer acid in an amount of 38% by
mass and having an MFR of 120 g/10 min and a softening point of
93.degree. C. was used as the raw material polyamide (2). A very
low-density polyethylene (VLDPE) (C) having an MFR of 30 g/10 min,
a melting point of 65.degree. C., and a specific gravity of 0.870
g/cm.sup.3 was used as the very low-density polyethylene. In each
of the adhesive resin composition Nos. 12 to 14, 10 parts by mass
of an oxidation inhibitor was added relative to 100 parts by mass
of the resin component.
[0120] The resin component and the additive were sufficiently mixed
to prepare the adhesive resin compositions. Each of the adhesive
resin compositions was irradiated with an electron beam so that the
absorbed dose was different. Thus, a plurality of adhesives were
obtained from each of the adhesive resin compositions. The absorbed
dose of the electron beam was adjusted to 100 kJ/kg, 200 kJ/kg, 300
kJ/kg, 400 kJ/kg, and 500 kJ/kg.
[0121] For each of the adhesives that were prepared by irradiating
the adhesive resin composition Nos. 12 to 14 with an electron beam
and that had different absorbed doses, a shear viscosity was
measured as in the adhesive resin composition Nos. 1 to 11. Table
VIII shows a shear viscosity of each of the adhesives at a shear
rate of 0.01 s.sup.-1. Table IX shows a shear viscosity of each of
the adhesives at a shear rate of 100 s.sup.-1.
TABLE-US-00008 TABLE VIII Shear viscosity (Pa s) Adhesive resin
composition (Shear rate: 0.01 s.sup.-1) No. 12 No. 13 No. 14
Absorbed 100 (KJ/Kg) 20 110 350 dose 200 (KJ/Kg) 660 320 730 300
(KJ/Kg) 2230 680 1520 400 (KJ/Kg) 3500 1080 2520 500 (KJ/Kg) -- --
--
TABLE-US-00009 TABLE IX Shear viscosity (Pa s) (Shear rate: 100
s.sup.-1) No. 12 No. 13 No. 14 Absorbed 100 (KJ/Kg) 10 60 50 dose
200 (KJ/Kg) 90 70 140 300 (KJ/Kg) 160 80 170 400 (KJ/Kg) 320 80 270
500 (KJ/Kg) -- -- --
[0122] As shown in Tables VIII and IX, regarding the adhesive resin
composition No. 12, when the absorbed dose of the electron beam was
200 kJ/kg or more and 300 kJ/kg or less, the shear viscosity at a
shear rate of 0.01 s.sup.-1 was 300 Pas or more, and the shear
viscosity at a shear rate of 100 s.sup.-1 was 200 Pas or less.
Thus, the adhesive resin composition had thixotropy suitable for an
adhesive for a multilayered heat-recoverable article.
[0123] Similarly, regarding the adhesive resin composition No. 13,
when the absorbed dose of the electron beam was 200 kJ/kg or more
and 400 kJ/kg or less; and regarding the adhesive resin composition
No. 14, when the absorbed dose of the electron beam was 100 kJ/kg
or more and 300 kJ/kg or less, the adhesive resin composition had
thixotropy suitable for an adhesive for a multilayered
heat-recoverable article.
[0124] Next, for each of the adhesives that were prepared by
irradiating the adhesive resin composition Nos. 12 to 14 with an
electron beam and that had different absorbed doses, the dripping
property test was conducted as in the adhesive resin composition
Nos. 1 to 11. Table X shows the dripping ratio of each of the
adhesives. Table XI shows a dripping property of each of the
adhesives.
TABLE-US-00010 TABLE X Dripping ratio Adhesive resin composition
(mass %) No. 12 No. 13 No. 14 Absorbed 100 (KJ/Kg) 70 16 0 dose 200
(KJ/Kg) 0 0 0 300 (KJ/Kg) 0 0 0 400 (KJ/Kg) 0 0 0 500 (KJ/Kg) 0 0
0
TABLE-US-00011 TABLE XI Dripping property Adhesive resin
composition evaluation No. 12 No. 13 No. 14 Absorbed 100 (KJ/Kg) B
B A dose 200 (KJ/Kg) A A A 300 (KJ/Kg) A A A 400 (KJ/Kg) A A A 500
(KJ/Kg) A A A
[0125] As shown in Tables X and XI, regarding the adhesive resin
composition No. 12, when the absorbed dose of the electron beam is
200 kJ/kg or more and 500 kJ/kg or less, the dripping ratio after
96 hours is 0%. Accordingly, it is evaluated that, even in a
multilayered heat-recoverable article, the adhesive does not easily
flow out from a base material layer. Similarly, regarding the
adhesive resin composition No. 13, when the absorbed dose of the
electron beam is 200 kJ/kg or more and 500 kJ/kg or less; and
regarding the adhesive resin composition No. 14, when the absorbed
dose of the electron beam is 100 kJ/kg or more and 500 kJ/kg or
less, it is evaluated that when the adhesive resin composition is
used as an adhesive for a multilayered heat-recoverable article,
the adhesive does not easily flow out from a base material layer
after heat shrinkage.
[0126] Furthermore, for each of the adhesives prepared by
irradiating the adhesive resin composition Nos. 12 to 14 with an
electron beam, waterproofing properties in multilayered
heat-recoverable articles were evaluated as in the adhesive resin
composition Nos. 1 to 11. Table XII shows evaluation results of
waterproofing properties of the adhesives.
TABLE-US-00012 TABLE XII Waterproofing property Adhesive resin
composition evaluation No. 12 No. 13 No. 14 Absorbed 100 (KJ/Kg) A
A A dose 200 (KJ/Kg) A A A 300 (KJ/Kg) A A A 400 (KJ/Kg) B A B 500
(KJ/Kg) B A B
[0127] As shown in Table XII, regarding the adhesive resin
composition Nos. 12 and 14, when the absorbed dose of the electron
beam was 100 kJ/kg or more and 300 kJ/kg or less; and regarding the
adhesive resin composition No. 13, when the absorbed dose of the
electron beam was 100 kJ/kg or more and 500 kJ/kg or less, the
adhesive had a good waterproofing property.
[0128] The above results show that when an adhesive resin
composition has a shear viscosity of 300 Pas or more at a shear
rate of 0.01 s.sup.-1 and a shear viscosity of 200 Pas or less at a
shear rate of 100 s.sup.-1, the adhesive resin composition has both
a good dripping property and a good waterproofing property and has
characteristics suitable for an adhesive for a multilayered
heat-recoverable article.
INDUSTRIAL APPLICABILITY
[0129] The multilayered heat-recoverable article of the present
invention, and the wire splice and wire harness that use the
multilayered heat-recoverable article have high adhesiveness to an
adherend because an adhesive moderately flows during heat
shrinkage, and have high reliability because the adhesive does not
easily flow out after heat compression.
REFERENCE SIGNS LIST
[0130] 1, 1A multilayered heat-recoverable article [0131] 1a tube
[0132] 10, 10A base material layer [0133] 11, 11A adhesive layer
[0134] 2 wire splice [0135] 20 wire [0136] 21 conductor wire [0137]
3 wire harness [0138] 30 wire [0139] 31 multi-pin connector [0140]
A sheet-like adhesive [0141] P glass plate
* * * * *